
#include "re_config.h"
#include "pcre_internal.h"

/*************************************************
 *         Flip bytes in an integer               *
 *************************************************/

/* This function is called when the magic number in a regex doesn't match, in
order to flip its bytes to see if we are dealing with a pattern that was
compiled on a host of different endianness. If so, this function is used to
flip other byte values.

Arguments:
  value        the number to flip
  n            the number of bytes to flip (assumed to be 2 or 4)

Returns:       the flipped value
*/

static unsigned long int byteflip(unsigned long int value, int n) {
    if (n == 2)
        return ((value & 0x00ff) << 8) | ((value & 0xff00) >> 8);
    return ((value & 0x000000ff) << 24) | ((value & 0x0000ff00) << 8) |
           ((value & 0x00ff0000) >> 8) | ((value & 0xff000000) >> 24);
}

/*************************************************
 *       Test for a byte-flipped compiled regex   *
 *************************************************/

/* This function is called from pcre_exec(), pcre_dfa_exec(), and also from
pcre_fullinfo(). Its job is to test whether the regex is byte-flipped - that
is, it was compiled on a system of opposite endianness. The function is called
only when the native MAGIC_NUMBER test fails. If the regex is indeed flipped,
we flip all the relevant values into a different data block, and return it.

Arguments:
  re               points to the regex
  study            points to study data, or NULL
  internal_re      points to a new regex block
  internal_study   points to a new study block

Returns:           the new block if is is indeed a byte-flipped regex
                   NULL if it is not
*/

real_pcre* _pcre_try_flipped(const real_pcre* re,
                             real_pcre* internal_re,
                             const pcre_study_data* study,
                             pcre_study_data* internal_study) {
    if (byteflip(re->magic_number, sizeof(re->magic_number)) != MAGIC_NUMBER)
        return NULL;

    *internal_re = *re; /* To copy other fields */
    internal_re->size = byteflip(re->size, sizeof(re->size));
    internal_re->options = byteflip(re->options, sizeof(re->options));
    internal_re->flags = (pcre_uint16)byteflip(re->flags, sizeof(re->flags));
    internal_re->top_bracket =
        (pcre_uint16)byteflip(re->top_bracket, sizeof(re->top_bracket));
    internal_re->top_backref =
        (pcre_uint16)byteflip(re->top_backref, sizeof(re->top_backref));
    internal_re->first_byte =
        (pcre_uint16)byteflip(re->first_byte, sizeof(re->first_byte));
    internal_re->req_byte =
        (pcre_uint16)byteflip(re->req_byte, sizeof(re->req_byte));
    internal_re->name_table_offset = (pcre_uint16)byteflip(
        re->name_table_offset, sizeof(re->name_table_offset));
    internal_re->name_entry_size =
        (pcre_uint16)byteflip(re->name_entry_size, sizeof(re->name_entry_size));
    internal_re->name_count =
        (pcre_uint16)byteflip(re->name_count, sizeof(re->name_count));

    if (study != NULL) {
        *internal_study = *study; /* To copy other fields */
        internal_study->size = byteflip(study->size, sizeof(study->size));
        internal_study->options =
            byteflip(study->options, sizeof(study->options));
    }

    return internal_re;
}

/* End of pcre_tryflipped.c */
